every single article has said it's a torn LCL.
as to his game being built on reaction time and that means ultimately his game won't suffer, not sure that makes sense. He does have pretty incredibly athleticism. he has a burst to the ball that you don't often see which makes his reaction time even better then most players. that could suffer in the long run.
Torn is always a generic term so I discount it until you hear the MRI results but I see now the results of the MRI say torn...that's conclusive. Also see he's going to have surgery in 10 days, which is good.
When it comes to the recovery time, the two together isn't that significantly different than one alone. The strength and rehab processes are similar, muscles are also similar to be restrengthened. The clean meniscus is very good, because that is where those "nagging" injuries come from. A ten day wait for surgery to get the swelling down is not a significant timeframe. Initial comments suggested it was waiting for LCL to heal for surgery...waiting for swelling isn't uncommon afaik.
As for it not affecting his game...sure, it is going to have some level of impact but I contend it isn't speed that gives him that burst, its the instantaneous diagnosis. That makes him appear faster than normal. He IS athletic, there's no doubt, and there's always a chance to lose the athleticism. But there are more athletic defenders than him out there that don't have remotely his talent level, because he's just instinctively perfect out there. His actual twitch and reaction time won't be affected, but he might be a small fraction of a second slower in getting to the ballcarrier than he was before...but not enough to take away the advantage his brain provides. Plus, he's a pretty damn hard worker, so I don't expect an impactful athletic step backwards.
Now, put him back there to return punts and you MIGHT see him gunshy, because it's much different taking the hit than giving it when it comes to an injury like that.